7189's vs EL84's
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- mojohand
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7189's vs EL84's
Would using a good matched pair of NOS 7189's (like maybe Sylvania blackplates, or Amperex, or GE) provide any improvement in an amp that normally uses EL84's?
I've read these make a good upgrade in lo watt (15 to 20 watt) amps using EL84's.
Anyone have any opinions, or experience with this?
Thanks.
I've read these make a good upgrade in lo watt (15 to 20 watt) amps using EL84's.
Anyone have any opinions, or experience with this?
Thanks.
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- T-bones
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Mojohand, this one can be tuff. 7189 handles some extra heat in certain amp circuits. The pros here can give it to you more defined than me. I do know if you play out nightly the 7189 will last you longer when using them in a circuit as the 18 watt Marshalls and AC-15's etc. I do really think the 6BQ5 in it's original format at it's proper running voltage sounds more robust with those plates just showing a little pink, thats the sweet spot for me. The black plates are good tubes, I have used them in the past and have been pleased with them. The Sarge has these 7189's he's been given a top billing too, I was thinking about trying a pair. I would warn a lot of NOS power tubes can be fussy with some of these higher plate voltages and short so it's a gamble either way you go. But if I had to pick one I'd favor the 6BQ5 just my opinion. I'm sure you will get some good answers on this site. T-bones.
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Personally I doubt that NOS tubes are any weaker than modern made ones - and in some cases I would think the opposite would apply, as I'm pretty sure that the quality control in the Mullard or RCA factories was a lot stricter than in many of today's Eastern Europen and Chinese plants. The real issue is that we want to wrap our last few precious Mullards in cotton wool and use them carefully, because once they're worn out, they're gone forever. Anyway 7189s and 7189As will last out much better with the abuse Marshall 18W, Vox and Matchless amps give, and will generally tend to give a more robust (ie less bright/glassy) tone.T-bones wrote:The Sarge has these 7189's he's been given a top billing too, I was thinking about trying a pair. I would warn a lot of NOS power tubes can be fussy with some of these higher plate voltages and short so it's a gamble either way you go.
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Nature abhors a clean tube amp
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The big difference between NOS 7189s and NOS 6BQ5/EL84s is the different plate voltage rating, 7189s were designed to work in ultralinear hi-fi amps with up to 400 volts on the plates and nearly that connected to the Grid 2 taps on the OT. NOS 6BQ5s are rated to live happily with around 300 volts on the plates.
The JJ 6BQ5/EL84s blur the line between 6BQ5s and 7189s, the JJs will happily handle higher plate voltages than many NOS types.
The difference in ratings usually mean that 6BQ5s have less "headroom".
A torture chamber for 6BQ5s tubes would be the Snyder "18 watt" amp sold by Hi-Test in New Jersey. There's one mode on that thing where it's fixed bias with close to 400 volts on the plates, good thing Hi-Test sells NOS tubes... it seems to me that the Snyder was designed to be re-tubed a lot more frequently than more conservative designs. Compare it to the old Jim Kelly FACS which eats 6V6 tubes like they're potato chips!
The JJ 6BQ5/EL84s blur the line between 6BQ5s and 7189s, the JJs will happily handle higher plate voltages than many NOS types.
The difference in ratings usually mean that 6BQ5s have less "headroom".
A torture chamber for 6BQ5s tubes would be the Snyder "18 watt" amp sold by Hi-Test in New Jersey. There's one mode on that thing where it's fixed bias with close to 400 volts on the plates, good thing Hi-Test sells NOS tubes... it seems to me that the Snyder was designed to be re-tubed a lot more frequently than more conservative designs. Compare it to the old Jim Kelly FACS which eats 6V6 tubes like they're potato chips!
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- zaphod_phil
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Those 7189s and 7189As are tough as hell, as also are EL84Ms. However, despite what the ratings say, El84/6BQ5s can also take 400V and above, provided their screen voltage is held at or below 300V and that their max dissipation rating isn't exceeded. For a while Seymour Duncan used to make a 50W amp which had a quad of EL84s, running at 560V. Now that's what you calla torture chamber! The trick was that they had a screen voltage of only 280V. Having said that, I think they would have had to burn-in test their tubes very thoroughly before using them in the amp.
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For me this is really simple, "cut and dried".
When it comes to NOS 6BQ5/EL84s, I run 'em at relatively conservative supply voltages, after all, the reason we're using EL84s to begin with is for cranked tube amp tone at less than earsplitting volumes. That's not to say that a cranked 18 watter won't make your ears ring, that's a different topic.
Sure, upping the supply voltage on EL84s will yield a tiny bit more power BUT if you're looking for more use quartets of EL84s. More EL84s equals more power. Simple.
If my B+ rail is over 350 volts I use 7189s, 6973s or 6V6s, the tone will be different. It seems to me to be a waste of good EL84s to "make it take it" at voltages over design maximum ratings. You can get away with voltages over design maximum ratings... for a while. I find that EL84s "cook" quickly enough even at conservative voltages.
Over 350 volts I'll reach for 5881s or EL34s.
When it comes to NOS 6BQ5/EL84s, I run 'em at relatively conservative supply voltages, after all, the reason we're using EL84s to begin with is for cranked tube amp tone at less than earsplitting volumes. That's not to say that a cranked 18 watter won't make your ears ring, that's a different topic.
Sure, upping the supply voltage on EL84s will yield a tiny bit more power BUT if you're looking for more use quartets of EL84s. More EL84s equals more power. Simple.
If my B+ rail is over 350 volts I use 7189s, 6973s or 6V6s, the tone will be different. It seems to me to be a waste of good EL84s to "make it take it" at voltages over design maximum ratings. You can get away with voltages over design maximum ratings... for a while. I find that EL84s "cook" quickly enough even at conservative voltages.
Over 350 volts I'll reach for 5881s or EL34s.
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Well 50W out of quartet of EL84s is more than tiny imcrease in power, vs the 30W or even 36W, you get out of a more standard design amp. Anyway, I wasn't advocating that it was necessarily a good idea, or that the tone would be great - just that it could be done, and the fact that EL84s will handle much more voltage than people think, given a couple of provisos. As for 18W amps they run their EL84s above both rated voltages and dissipation. As one of my amps has NOS Mullards, I have applied Jason's Screen/PSU mods, to keep things a little gentler on those tubes.
Anyway, what were we talking about? Oh yes, 7189s, what great tubes!
Anyway, what were we talking about? Oh yes, 7189s, what great tubes!
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"Well 50W out of quartet of EL84s is more than tiny increase in power, vs the 30W or even 36W"
Yeah but... due to the logarithmic nature of increased power versus sound pressure level from any particular speaker the extra watts don't buy you much, and you're paying in decreased tube life.
My point is that if you're stuck with a particular power supply that's hard on EL84s reach for 7189s, they're designed to perform under more demanding conditions. If you want "EL84 tone" engineer an environment where you achieve optimum tube life.
Just because certain vintage amps were designed with voltages beyond published maximums isn't a good reason to create a similar situation with modern "reproductions". Think of how inexpensive Mullard EL84s were when Marshall used 'em as original equipment! Burn 'em up and toss 'em out! Well, not at $75.00 a pair and up these days!
I would expect the excessive voltages in the Duncan amps was due to limited transformer availability in the '80s. Those things were brilliant in concept but less than brilliant in execution.
Yeah but... due to the logarithmic nature of increased power versus sound pressure level from any particular speaker the extra watts don't buy you much, and you're paying in decreased tube life.
My point is that if you're stuck with a particular power supply that's hard on EL84s reach for 7189s, they're designed to perform under more demanding conditions. If you want "EL84 tone" engineer an environment where you achieve optimum tube life.
Just because certain vintage amps were designed with voltages beyond published maximums isn't a good reason to create a similar situation with modern "reproductions". Think of how inexpensive Mullard EL84s were when Marshall used 'em as original equipment! Burn 'em up and toss 'em out! Well, not at $75.00 a pair and up these days!
I would expect the excessive voltages in the Duncan amps was due to limited transformer availability in the '80s. Those things were brilliant in concept but less than brilliant in execution.
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- zaphod_phil
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Hmmm, I think you're arguing against some points that I wasn't actually making. I was just pointing at that it is *possible* to run EL84s at these voltages, not that it's to be greatly recommended. IMO the bottom line is that it's actually the power dissipation you run them at, which will wear them out, more than the B+ voltage. The effect of too high a B+ voltage for a tube is arc-over.
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- sgtoverdrive
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i got rid of all the nos rca ,slys and various other 7189 after i heard the russian eb,i will add this beware of the ebs that circulate around there are about 4 different years these tubes were exceptional.the rest belong in russky color tvs although they will last forever so does the grainy tone that so often accompanys them. ive seen even older batches that sound just awful 78 to 81 respectivily.the good ones are generally the 83 3 5 7 and these tubes in bulk have gone up 200 percent in the last 4 months .my best price in europe is 8 dollars a piece and thats for 200 pieces. this is due to our dollar being next to the peso over there.gee and we saved em from goose stepping and this is what we get!!!! the sgt thinks we have unfinished biz over there.....give em hell boys over the top nobody lives forever!!! by the way still have dead matched sets of the aforementioned for 35 measly bucks.i love this tube and use it most all the time in my 2 18s
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Actually 7189s only have a dissipation rating of 12W like a regular EL84, but are designed to take higher voltages. 7189A's are the ones rated for 13.2W dissipation. You also need to be careful with those, as they have a slightly different pin configuration than EL84s.
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Re: 7189's vs EL84's
I know this is an old thread, but I really need to say that people shouldn’t waste their good money on matched power tubes. I once bought a pair, when I didn’t know better, and the amp sounded somewhat sterile compared to when I used a non-matched pair. Matched tubes are really only needed for hi-fi, not guitar amps. Non-matched tubes help generate nice, warm sounding even-order harmonics. The great legendary guitar amp companies of the past also didn't use matched tubes, and just put in tubes as they pulled them out the box.
Here's what really blew my mind, I once used a couple of random Russian-made 6V6 tubes in a prototype of a commercial amp build. They were just in my tube stash and were even dated several years apart from each other. However, the amp worked flawlessly and sounded excellent!
7189 tubes are a very good substitute for EL84s, even though they are actually beam tetrodes, while EL84s are true power pentodes. 7189s and 7189As are like rugged EL84s and are therefore typically used in heavy-duty applications like organ amplifiers. Note that the 7189A version has a different pinout. Unfortunately, I’ve never had the chance to A/B test 7189s against EL84s for tone.
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Re: 7189's vs EL84's
interesting point about the matched tubes ZP,the output transformer also plays a part i.e. my hammond 1750PA has unequal resistance on the primary so even if i fit an exactly matched pair of tubes there is a difference of about 1/2 watt dissipation between them when biased.
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